1. Field of the Invention
The present invention relates to the field of separating certain mineral components of an ore from other mineral components of the same ore using electrostatic separation. Specifically, the present invention relates to electrostatic modification reagents and methods of using them in an electrostatic separation process to separate the mineral components within the ore with improved efficiency.
2. Description of the Related Art
Processing and refining many types of mineral ores, including mineral sands, sometimes known as beneficiation, generally involves the separation of certain mineral components from other mineral components.
For example a single ore or mineral sand may typically include both rutile and zircon. Both of these mineral have independent uses and must be separated from one another. Such a mineral sand may also include ilmenite, monazite, quartz, staurolite and leucoxene, which also must be separated form the rutile and zircon. Electrostatic separation is widely used in the heavy mineral ore or sand industries. An electrostatic separator applies a voltage typically in the range of 21 to 26 kV across the ore resulting in conductive components such as rutile and ilmenite to migrate to one end of the separator and the non-conductive components such as zircon to migrate to an opposing end of the separator. The stream of ground ore or mineral sand is split into two streams and each stream can be further processed to separate out its respective components using for example magnetic separation. While electrostatic separation is an effective process, it is not considered to be highly efficient.
U.S. Pat. No. 4,131,539 to Ojiri, et al. discloses a method for removing small amounts of rutile from zircon sand. This patent teaches heat treating the zircon sand in a non-oxidizing atmosphere in order to alter the surface electrostatic property of the rutile which is said to make rutile more conductive and the heat treated sand is more easily separated by electrostatic separation to reduce the titanium dioxide content of the sand. While such heating or roasting can be effective, it is energy intensive and alters the surface properties of the mineral components that may not be desirable in the down stream applications.
U.S. Pat. No. 5,502,118 to Macholdt et al. teaches the use of polymeric salts that are suitable as charge control agents and charge improvers in electrophotographic toners and developers, in triboelectrically or electrokinetically sprayable powder coatings, in electric materials and for the electrostatic separation of polymers and salt minerals. This does not however pertain to the enhanced separation of mineral components.
In one mineral separation processes, such as that shown in U.S. Pat. No. 6,168,029 to Henderson et al., which purports to increase the efficiency of the process, anionic copolymers of acrylic acid and acrylamide reagents are used. A need thus still exists for an improved, more efficient reagent and method for separating conductive mineral components from non-conductive mineral components of a common ore or mineral sand. Such improved separation could be applicable not only to the mining of rutile and zircon, but to any other ore that includes both non-conductive and conductive components having a commercial value